Fuse



l2 Sheets-Sheet l T. BIRKENMAIER FUSE Filed April 7.1958r Nav. s, 1938.Y

` FIGJ.

Nov. 8, 1938. T. BIRKENMAIER FUSE Filed April 7, 1958 2 Sheets-Sheet 2CFI APatented Nov. s, 193s UNITED STATES FUSE.

Theodore Birkenmaier, St. Louis, Mo., assgnor to W. N. MatthewsCorporation, St. Louis, Mo., a corporation of Missouri Application April7, 1938, .Serial No. 200,590

23 Claims.

This invention relates to fuses, and with regard to certain morespecific features, to expulsion fuses. l

This invention is an improvement upon the construction disclosed in myUnited States Patent 2,077,207, dated Apru 13, 1937.

Among the several objects of the invention maybe noted the provision ofmeans for obtaining the objects set forth in the above-named patent butby use of the knife type of contacts, rather than by the cantileverspring type of contacts of the patent;` the provision of apparatus ofthe class .described which eliminatesv the necessity for anyterminal-engaging element being movable on the door; and the provision.of a switch of the class described which is even more reliable than theswitch of the patent. Other objects will be in part obviousandinpartpointed out hereinafter.

The invention accordingly comprises the elewhich will be indicated inthe following claims.

. In the accompanying drawings, in which is illustrated one of thevarious possible embodiments of the invention- Fig.'1 is a verticalsection showing the invention fused and in circuit-closing position;

Fig. 2 is a view similar to Fig. '1, but showing a first movement as adisconnection occurs;

Fig. 3 is a view similar to Fig.'2 showing a final position of partsafter disconnection;

Fig. 4 is an inside view of the door with the fuse parts thereon in theposition such as shown in Fig. 1;

Fig. 5 is a horizontal section taken on line 5--5 of Fig. 1; l

Fig. 6 is a horizontal Asection taken on line' 6 6 of Fig. 1;'and,v

Fig. 'I is a horizontal section taken on line 1-1 of Fig. 4. l

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.,

In my Patent 2,077,207, I show an expulsion fuse construction in whichthe fuse link, after melting, and after being expelled from a fuse tube,hangs from the fuse unit in an unelectrified condition, with a wideseparation of the link separated ends. While the apparatus of thatpatent is effective, it is desirable, under certain circumstances, toemploy a so-called knife contact means. For example, where alow-temperaturerequired movement of the lower .terminal-en- 10 gagingelement.

It is furthermore true thaty in general a pair of relatively xedterminal-engaging elements for engagement with a pair of fixed lineterminals is preferable, because of its simplicity, to a constructionwherein one or more of these terminals or elements is movable withrespect to the other in responseV to circuit-breaking action..

Referring now more particularly to Fig. 1, there is shown atnumeral i abox made of in-l sulating material such as porcelain adapted to b'esupported by means of; bolts 3 and having anchored therein conductingline terminals 5. The line terminals include wire clamps 1 forrespective wires 8 (Fig. 6) and riveted U-shaped spring conductingmembers forming so-called knife contacts 9.

The box I is open at the bottom as indicated at I I, and has a frontopening I3 covered by a door I5 hinged on a pin I1. The hook-shaped.portion I9 on the door which eiects hingingl is open as shownV at 2iso.that the door may be removed from the box after it has been pulledftoan open position. Aring 23 is provided for pulling the door open. Thedoor I5 is also made of insulating material, such as Bakelite, forexample. y The door I5 has attached thereto, by means of screws 25,upper and lower terminal-engaging elements 21 and 29 respectively. Theseterminal-engaging elements 21 and 29 are made of conducting materialandA are hollow and have Afiat sides 3l and 33 for engagement with theat sides of the U-shaped spring conducting blades or clips 9.

The spring pressure betweenl the clips 9 and A the terminal-engagingelements 21 and 29 isv relatively high, so that a good contact isobtained without undue Ytemperature rise in the switch under operatingconditions. This also induces friction which maintains the door I5 inclosed condition but which permits of pulling the door open, whendesired. 1

The hollow portion of the upper terminal-engaging element 21 is open atthe top and bottom, and at the top is threaded-to receive a threadedenclosing cap 35. The cap also functions as a clamp for the upperheaded-end 31 of a fuse link fili. The fuse link 35i has a reducedportion 4l adapted to melt upon overload and to open the circuit. nitslower end is composed of flexible conducting wire, as indicated at d3.

The fuse linl; 3S, di passes through an insulat- This tube l5 passesdownwardly in spaced relation to and through the hollow lowerterminal-engaging element 29. t is also supported in an extension 25from the door l5. The lower end or' the tube is open, as indicated atfl'l, and has an open notch -flS at one side. A septum associated withthe box forms a saddle around the tube and with the adjacent support 2Sdivides the bos roughly into an upper and lower compartment, to tend toprevent current leakage between the line terminals E. l

Slidsbly arranged on the insulating tube :i5 is a second insulating tubeor sleeve 5IY which is also 'ole through the hollow lowerterminal-enelernent J. is prevented from turning in the hollowcylindrical form of the element .2S by :cleans of groove 53 therein,with which cooperates a pin the terminal-engaging element. This pin whencontacted by the upper end of the groove also limits the downwardmovement of the sleeve or tube iii, as indicated Fig.

The lower end of the sleeve 5i is provided with hired collar il? whichmay or may not be made of conducting although in the present embodimentit is so shown. This collar is formed on one side with a smooth,rounded, anti-friction saddle Tillle notch il@ in fixed tube d5cooperates with the inner edge of the saddle E9 ss shown in Fig. l toprevent interference beeen the lower end o the tube it and the fuse 'topof se collar di forms a seat for a above the spring Si and slidably arngsleeve or contact Sd. This sleeve or contact carries a pin i5 whichslides in said groove so sliding of contact is permitted, but rotationis prevented lf the sleeve El be pushed upwardly, the conducting sleeveencounters the lower terminal-engaging element 29 to make a goodcontact. Further upward movement of the sleeve di results in a xedshoulder 51 thereon compressing the spring Si, so that the contact it istightly biased and held against the stationary terminal-engaging element29.

The outside of the pin E5 forms a threaded post for reception of athumb-nut 68 and washer 'l2 for clamping the looped end portion of thefuse d3.

Operation of the device is as follows, assuming that the door l5 hasbeen removed, and that a. new ruse is required:

The cap is removed and any old upper fuse element removed. The same'istrue of such lower fuse element as may be under the nut 68 and washer1S.

l ie new fuse is fed (flexible part first) through the upperterminal-engaging element 21 and. its head 3l' is clamped in position bythe enclosing cap 35. The lower end of the fuse then extends from theopening l1 and from the lower open end E? of the ring 51. It is threadedaroundthe saddle '59 and then pulled upwardly until the conductingcontact- G3 is pushed up against the termined-engaging element 29. Thepulling is then continued until compression is placed in the ing tubedii which is rigidly supported at its upat the saddle spring 6 i, thusforcing the contact 63 and element 29 together. The flexible end of thefuse link is then wrapped around the post 6B and nut 68 tightened down.

From Fig. 4 it will be seen that the lower end oi the groove 53 isnormally not far from the pin S5, so that there is a linut to which thespring 5l may compressed by pulling up on the saddie 5S with the portion13 of the fuse link.

From the above, it will be seen that the spring 5l in tendingto expandreacts to push down the saddle 59 to place tension in the fuse, but atthe same time it holds the sliding Contact 53 against the lowerterminal-engaging element 29. II, then, the door has its hook i9 appliedto the pin il and is rotated into the position shown in Fig. l, theterminal-engaging elements 21 and 2?: will engage the line terminals 9in knife fashion and the door will be held shut while the circuit isclosed through the fuse (Fig. l).

Upon overload, the reduced portion 4| melts and the fuse is at irstdrawn down by the pull 59 caused by the expansion of the now releasedspring 5l (see Fig. 2). If, as often occurs under conditions of heavyoverload or short circuit, there is an ez'pulsive action, the effeet isto blow the entire link i3 from the tube 55, and finally the conditionof Fig. 3 is reached wherein graty causes the assembly of the contactte, sprinff 5l, ring 51 and sleeve 5l to continue downwardly' until.limited by the action of the pin 55 at the upper end of the groove 53,the flexible part of the link in the meanwhile having been drawn outover the smooth saddle 59 as indicated in Fig. 2. Finally, the linkfalls entirely out of the tube.

Upon small or so-called dragging overloads, even a relatively ilegibleportion such as 43 may remain in tie tube l5 after expansion of thespring Gl, but it has n greater separation than shown in Fig'. 2,because of the substantial drop which occurs in the tube 5l inmovingirom the position shown in Fig. 2 to that shown in Fig. 3. Thus,although flexibility is desirable in the portion t3, it will be seenthat it is not absolutely necessary', and that various degrees offlexibility will be suitable. Furthermore, the invention is even usefulwith relatively stiff fuse links, because in such cases, although thebent link cannot slide over the saddle 59, nevertheless, when itseparates, the upward reaction of the spring 61 on Contact 53accelerates the tube 5| downwardly and gravity further aids the downwardmotion, until a relatively wide separation of the ends of the fuse linkis effected.

The ultimate result is that the lower fragment of the fuse linkwhich isleft may hang from the boxt but is electrically dead, because thecontact B3 has separated under the gravity action from' the lowerterminal-engaging element 29. It will be seen that the action isindependent o! any motion of the lower line terminal or of theterminal-engaging element 29, and thus distinguishes from theconstruction shown in said Patent 2,077,207.

Another distinction is in the provision of the saddle 59 and the notch49 adjacent the saddle 59. The notch 49 permits the lower iiexibleportion 43 of. the fuse link to reach the smooth, hard surface of thesaddle 59 without contacting the side of the opening 41 of the innertube 45. Thus, the retardlng action of friction (the saddle 59 being ofthe nature of an anti-friction device) is reduced. It will be understoodthat, if desired,

the saddle 59 may be replaced by'an equivalent wheel, roller or thelike. v

Another feature distinguishing the invention from that shown in saidPatent 2,077,207 is that the contact 4 between the lowerterminal-engaging element 29-and the lower line terminal 9 isindependent of the spring ,which provides the tension in the fuse link.Thus the problems of proper electrical contact'pressure may be solvedindependently of `the problem of operating pressures required for properautomatic operation.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in carryingv out the above constructionswithout departing from thescope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

I'claim:

1. In apparatus of the class described, a pair of relatively fixedterminal-engaging elements, a contact movable with respect to one ofsaid terminal-engaging elements, a fuse link fastened `to the contact,said fuse link passing to a connection with one engaging element, meanspressing the fuse link between its ends, and expansive means betweensaid contact and said pressing means adapted both to force said pressingmeans to tension said link and to force said contact against the otherterminal-engaging element.

2. In apparatus of the class described, spaced line terminals, a fusedsupport, a pair of fixed terminal-engaging elements on said support andcooperating respectivelyiwith said line terminals,

a contact movable with respect to one of said terminal-engagingelements, a fuse fastening 4means on the contact, a fuse link passingfrom ing element fixed on the support and a contact movable with respectthereto, a fuse fastening means on the contact, a fuse link passing fromthe first engaging element through said second engaging element andthrough and to the contact, the contact being movable and held inengagement with the second-named engaging element by the unfused link,and being separable therefrom by gravity when the link fuses.

4. In apparatus of the class described, spaced line terminals, a fusesupport, a 'terminal-engaging element fixed on sai-d support andcooperating with one line terminal, another terminal-engaging elementiixed on the support and a 'contact movable with respect thereto, a fusefastening means on the contact, a fuse link passing from the*vl firstengaging element and to the contact,

the contact being movable and held by the unfused link in engagementwith thesecond-named engaging element, and being separable by gravitywhen the link fuses, and means reacting between said contact and thelink to tension the latter.

5. In apparatus of the class described, spaced line terminals, a fusesupport, a terminal-engaging element fixed on said support andcooperating with one line terminal, another terminal-engaging elementfixed on the support and a co/ntact movable with respect thereto, a fusefastening means on the contact, a fuse link passing from the firstengaging element and to the contact, the contact being movable and heidby the unfused link in engagement with the second-named engagingelement, and being separable by gravity when the link fuses, and springmeans reacting between said contact and the link to tension the latter,saidspring means being adapted to be tensioned by shortening of the fusewhenthe latter is attached to the contact.

6. A fuse comprising a fuse holder, a terminalengaging element at oneend of said holder, said' holder being open at the other end, a slidablemember on said holder, said slidable member having an open end normallyadjacent the open" end of the holder, a fuse contact slidable on saidmember, a fuse joining said last-named contact and saidterminal-engaging element, and resilient means reacting between themember and said contact thereon.

7. A fuse comprising a fuse engaging element at one end of said tube,said tube being open at the other end, a second slidable tube onsaidfirst tube, said second tube having an open end normally adjacent theopen end of the rst tube, a fuse contact slidable on said second tube, afuse joining said last-named contact and said terminal-engaging element,re-

` silient means reacting between points at the end of said slidable tubeand said`contact thereon, and a second terminal-engaging 'elementadapted to be contacted by the contact upon movement of the slidabletube toward the first-named terminal-engaging element by shortening ofthe link. 8. In a fuse, a fixed fuse tube, a terminal at one end of saidtube, said tube being open at the other end, a slidable tube on saidrsttube adjacent the open end, said slidable tube having an open endnormally adjacent the open end of the rst tube, a second terminal, acontact slidable on the slidable tube and lying outside the reachbetween the two terminal elements, a fuse fastened to the terminalelement and extending through the fixed tube and of a length to hold theslidable tube in a position to force the Contact against the secondterminal element, and resilient means reacting between the contact and aportion associated with the slidable tube.

9. In a fuse, a xed fuse tube, a terminal at one end of said tube, saidtube being open at the other end, a slidable tube on said rsttubeadjacent the open end, said slidabletube having an tube, a terminalopenend normally adjacent the open end of the v first tube, a secondterminal, a contact vsl'idable on the slidable tube and lying outsidethe reach between the two terminal elements, a fuse fasassociated withthe insulating tube, and a con-` tact slidable on said telescoping tubeand engageable with the second-named xed terminal-engaging element.

ii. A fuse comprising an insulating tube, a terminal-engaging elementnear one end ci said tube, a second terminal-engaging element near theother end o the tube, a telescoping and insulating tube associated withthe insulating tube, a Contact slidable on said telescoping tube andengageable with the second-named terminal-engaging element, andresilient means adapted to react between the slidable contact and tlietelescoping tube.

l2. A fuse comprising an insulating tube, a terminal-engaging elementnear one end of said tube, a second terminal-engaging element near theother end ci tne tube, a telescoping and insulating tube associated withthe insulating tube, a contact slidable on said telescoping tube andengageable Witn the second-named terminal-engaging element, resilientmeans adapted to react between the slidable Contact and tbe telescopingtube, and a link joining the contact and firstnamed terminal-engagingelement, said lir being of a length to tension said resilient means toreact.

i3. A fuse comprising an insulating tube, a iixed terminal-engagingelement enclosing one end oi said tube, a second xed terminal-engagingelement near tbe other end of the tube, a telescoping and insulatingtube associated 'with the iixed insulating tube, a contact slidable onsaid telescoping tube and engageable with the second-named unedterminal-engaging element, a fuse link joining the rst-namedterminal-engaging element and said contact, anti-friction means at tbeend of said slidab-le tube adapted toy be contacted by 'tbe link, andresilient means reacting from the end of said tube and said contact.

lei. A fuse comprising a fuse holder, a terminalengaging element on saidholder, a second terminal-engaging element, an insulating sliding memberassociated with the holder, and a contact slidable on said slidingmember and engageable with the second terminal-engaging element.

15. A fuse comprising a fuse bolder, a terminal-engaging element on saidbolder, a second terminal-engaging element, an'insulating sliding memberassociated with the holder, a contact slidable on said sliding memberengageable with the second terminal-engaging element, and resilientmeans reacting between the sliding member and the contact.

16. A fuse comprising a fuse holder, a terminai-engaging element on saidholder, a second terminal-engaging element, an insulating sliding memberassociated with the holder, a. contact slidable on said sliding memberengageable with the second terminal-engaging element, resilient meansreacting between the sliding member and the contact, and a fuse linkjoining the iirstnamed terminal-engaging element and the contact andforcing the sliding member to push the contact against the secondterminal-engaging element and to tension said resilient means.

i7. In a fuse, a nxed fuse tube, a xed terminal element at one end ofsaid tube, said tube being open at the other end, a second slidable tubeon said first tube adjacent the open end, said second tube having anopen end normally adjacent the open end of the rst tube, a second iixedterminal element, a movable contact on the slidable tube lying outsidethe reach between the two terminal elements, and a fuse adapted to befastened by the rst-named'terminai element and to extend through thefixed tube and to hold the slidable tube to force th Contact against thesecond terminai element, and means for tensioning said contact againstthesecond terminal element and for tensioning the fuse.

18. In apparatus of the class described, a box, a door on said box,upper and lower line terminais in said box, iixed terminal-engagingelements on said door for contacting said line terminals, an insulatingtube extending from said upper terminal-engaging element downwardly pastthe lower line terminal, a second insulated tube telescoping thenrst-tube, a resilient contact on said second tube adapted to fasten afuse and a link joining said last-named contact and the upperterminal-engaging element.

i9. In apparatus of the class described, a box, a door on said box,upper and lower line terminals in said box, a terminal-engaging elementon said door for said upper line terminal, an insulating tube extendingfrom said upper terminalengaging element downwardly past the lower lineterminal, a second insulated tube telescoping the rst tube, a contact onsecond tube adapted to fasten a fuse link, a linl; joining saidlastnamed contact and the tei'nal-engaging element, and a lower ixedterminal-engaging element on said door and adapted to beengaged by saidcontact when the contact is moved toward the upper terminal-engagelement, said link in normal position holding said contact against thelower terminal-engaging element.

2). In apparatus of tbe class described, a bon, a door on said box,upper and lower line terminals in said box, fixed terminal-engagingelements on said door for said line terminals, an insulating tubeextending from the upper terminal-engaging element downwardly past thelower line terminal, a second insulating tube telescoping the firsttube, a movable Contact on said second tube adapted tc a fuse link, alinl: joining said last-named contact and the upper terminal-engagingelement, the lower one of tbe terminal-engaging elements on said doorbeing adapted to be engaged by said Contact when the Contact is biasedtoward the upper terminalengaging element, said linie holding saidContact so biased, and resilient means reacting between the contact anda portion 'associated with the link.

2l. In apparatus of the class described, a box, a door on said box,upper and lower line terminals in said box, an upper terminal-engagingelement onsaid door for said upper line'terrninals, an insulating tubeextending from said upper terminal-engaging element downwardly past thelower line terminal, a second insulated tube telescoping the first tube,a contact on said second tube adapted to fasten a fuse link, a linkjoining said last-named contact and the first-named terminal-engagingelement, and a lower terminal-engaging element ilxed on said door andadapted to be engaged by said contact when the c ontact is moved towardthe upper terminalengaging element, and means reacting between saidContact and a portion of the fuse link to `tension said link and toforce said contact against the lower terminal-engaging element.

22. A fuse comprising a fuse holder, a ternorniai position mamas able onsaid member, a fuse joining said lastnamed contact and saidterminal-engaging element, resilient means reacting between the memberand said contact thereon, a second terminalengaging element with respectto which said slidable member moves, and means between the secondterminal-engaging element end the slidable member limiting downwardmovement of the latter.

23. A fuse comprising a fuse holder, a termined-engaging element at oneend ot said holder, said holder being open at the other end, e. slidablemember en said holder, said slidable member having an open end normallyadjacent' the open end of the holder, a fuse contact slidable on saidmember,I a fuse joining said lastnamed contact and saidterminal-engaging eiement, resilient means reacting between the meinberand said contact thereon, a second terminalengaging element with respectto which said slidahle member'moves. means between the secondterminal-engaging element and the slidabie member limiting` downwardmovement of the latter, and means between said fuse Contact and saidsldable member limiting the relative motion between the two in order tolimit the compression

